Optical apparatus

ABSTRACT

An optical system includes a plurality of internal apertures, a plurality of external optical assemblies and a telescope assembly positioned between the plurality of internal apertures and the plurality of external optical assemblies. Each internal aperture is operable to receive a corresponding aperture-specific optical signal. Each external optical assembly corresponds to one of the internal apertures, and each external optical assembly is operable to direct the aperture-specific optical signal of the corresponding internal aperture in a corresponding external direction. The external direction for each external optical assembly is independently controllable and the telescope assembly defines a shared optical train arranged to direct the aperture-specific optical signals between each internal aperture and the corresponding external optical assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/981,170 filed on Feb. 25, 2020, which is incorporated by reference herein in its entirety.

FIELD

The present subject-matter relates to optical systems, and more particularly to optical systems that include telescope assemblies.

INTRODUCTION

The following is not an admission that anything discussed below is part of the prior art or part of the common general knowledge of a person skilled in the art.

Satellite based telecommunication is increasingly being used to provide broadband communication across the globe. Telecommunication satellites can rapidly transmit data between locations on opposite sides of the globe, including locations on land, at sea and in the air. A number of satellite constellations are being launched in low earth orbit (e.g. One Web, Telesat LEO, Space X's Starlink, Amazon's Kuiper, etc.) to facilitate the transmission of data across the globe. There is an ongoing need to improve the communication capabilities of satellites used in telecommunication.

SUMMARY

The following introduction is provided to introduce the reader to the more detailed discussion to follow. The introduction is not intended to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub-combination of the elements or process steps disclosed in any part of this document including its claims and figures.

Satellite based telecommunications systems can provide point-to-point communication coverage across the planet. To facilitate communications over large distances, networks of satellites can be used to route communications. The satellites in these networks can be configured to communicate with neighboring satellites through optical inter-satellite links. To facilitate communication through these networks, each satellite can include multiple communication terminals (often four terminals) to provide links to multiple neighboring satellites.

In accordance with this disclosure, an optical system can be provided with a shared telescope assembly for a plurality of signal terminals. Each signal terminal may be used to transmit and/or receive signals. The plurality of signal terminals can share an optical train defined by the telescope assembly while still being capable of pointing in different directions. Each signal terminal may be independently adjustable to define the external signal transmission/acquisition direction for that terminal. Combining the optical trains for the different signal terminals can reduce the overall size and mass of the optical assembly required by the satellite. In addition, by providing a shared optical train assembly, manufacturing and testing of the optical system can be simplified.

In an aspect of this disclosure, there is provided an optical system comprising: a plurality of internal apertures, wherein each internal aperture is operable to receive a corresponding aperture-specific optical signal; a plurality of external optical assemblies, wherein each external optical assembly corresponds to one of the internal apertures, and each external optical assembly is operable to direct the aperture-specific optical signal of the corresponding internal aperture in a corresponding external direction, wherein the external direction for each external optical assembly is independently controllable; and a telescope assembly positioned between the plurality of internal apertures and the plurality of external optical assemblies, wherein the telescope assembly defines a shared optical train arranged to direct the aperture-specific optical signals between each internal aperture and the corresponding external optical assembly.

In some embodiments, the optical system may be an optical laser communication system.

In some embodiments, the shared optical train may include a parabolic mirror, and each external optical assembly may include an input sub-aperture arranged facing the same parabolic mirror so that each corresponding aperture-specific optical signal is reflected by the same parabolic mirror.

In some embodiments, the telescope assembly can define a central telescope axis, and the parabolic mirror may be concentric with the central telescope axis. In some embodiments, the parabolic mirror may be rotationally symmetric about the central telescope axis.

In some embodiments, the telescope assembly can define a central telescope axis, and the optical train may be rotationally symmetric about the central telescope axis.

In some embodiments, the optical train may include a plurality of optical elements, and the plurality of optical elements may be concentric.

In some embodiments, the optical train may include a plurality of mirrors, and the plurality of mirrors may be concentric.

In some embodiments, the optical train may include a plurality of lenses, and the plurality of lenses may be concentric.

In some embodiments, the optical train may include a plurality of mirrors, and each mirror may be rotationally symmetric.

In some embodiments, the optical train may include a plurality of lenses, and each lens may be rotationally symmetric.

In some embodiments, the optical train may include at least one lens and at least one mirror and the at least one lens and the at least one mirror may be concentric.

In some embodiments, the optical train may include at least one lens and at least one mirror and each lens and each mirror may be concentric.

In some embodiments, the telescope assembly may define a telescope field of view; and each external direction may have an angular separation from each and every other external direction that is controllable to an angular separation range greater than the telescope field of view.

In some embodiments, each external optical assembly may include an adjustable beam deflector operable to direct the corresponding aperture-specific optical signal through a corresponding external communication terminal in the corresponding external direction.

In some embodiments, the beam deflector may include a coarse pointing assembly.

It will be appreciated by a person skilled in the art that an optical system may include any one or more of the features contained herein and that the features may be used in any particular combination or sub-combination suitable for an optical system.

Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole.

DRAWINGS

For a better understanding of the embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings which show at least one exemplary embodiment, and in which:

FIG. 1A shows a perspective view of an example telescope assembly in accordance with an embodiment;

FIG. 1B shows a sectional view of the example telescope assembly of FIG. 1A in accordance with an embodiment;

FIG. 2 shows a sectional view of another example telescope assembly in accordance with an embodiment;

FIG. 3 shows a sectional view of an individual telescope portion of the example telescope assembly of FIG. 2 in accordance with an embodiment;

FIG. 4 shows a sectional view of another example telescope assembly in accordance with an embodiment;

FIG. 5 shows a sectional view of an example signal transmission terminal assembly;

FIG. 6 shows a perspective view of an example optical signal transmission system in accordance with an embodiment;

FIG. 7 shows a side view of the example optical signal transmission system of FIG. 6 in accordance with an embodiment;

FIG. 8 shows a top view of the example optical signal transmission system of FIG. 6 in accordance with an embodiment; and

FIG. 9 shows a bottom view of the example optical signal transmission system of FIG. 6 in accordance with an embodiment;

FIG. 10 shows a side view of the example optical signal transmission system of FIG. 6 with a transparent housing section in accordance with an embodiment; and

FIG. 11 shows a block diagram of an example signal transceiver unit in accordance with an embodiment.

DESCRIPTION OF VARIOUS EMBODIMENTS

It will be appreciated that, for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements or steps. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description is not to be considered as limiting the scope of the embodiments described herein in any way but rather as merely describing the implementation of the various embodiments described herein.

In the description and drawings herein, reference may be made to a Cartesian co-ordinate system in which the vertical direction, or z-axis, extends in an up and down orientation from bottom to top. The x-axis extends in a first horizontal or width dimension perpendicular to the z-axis, and the y-axis extends cross-wise horizontally relative to the x-axis in a second horizontal or length dimension.

The terms “an embodiment,” “embodiment,” “embodiments,” “the embodiment,” “the embodiments,” “one or more embodiments,” “some embodiments,” and “one embodiment” mean “one or more (but not all) embodiments of the present invention(s),” unless expressly specified otherwise.

The terms “including,” “comprising” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. A listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an” and “the” mean “one or more,” unless expressly specified otherwise.

As used herein and in the claims, two or more parts are said to be “coupled”, “connected”, “attached”, or “fastened” where the parts are joined or operate together either directly or indirectly (i.e., through one or more intermediate parts), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, “directly connected”, “directly attached”, or “directly fastened” where the parts are connected in physical contact with each other. As used herein, two or more parts are said to be “rigidly coupled”, “rigidly connected”, “rigidly attached”, or “rigidly fastened” where the parts are coupled so as to move as one while maintaining a constant orientation relative to each other. None of the terms “coupled”, “connected”, “attached”, and “fastened” distinguish the manner in which two or more parts are joined together.

Satellite based telecommunications systems can provide point-to-point communication coverage across the planet. Satellite communication links are being developed based on optical communication technologies rather than radio-frequency communications. The use of optical communication technologies provides orders of magnitude larger communication bandwidth as compared to RF communications and avoids difficulties associated with spectrum licensing. Optical communications are also very precise and do not diffract as much as communications using radio-frequency spectrum. To ensure that the communications are directed appropriately, the satellite optics (e.g. the telescope assembly within each satellite) need to be precisely manufactured and aligned. In addition, stabilization techniques may also be required to minimize or avoid jitter caused by the motion of the satellite.

Constellations of telecommunication satellites promise ubiquitous, high bandwidth and low-latency broadband coverage everywhere on the planet, in the air or at sea. These satellite constellations may include many hundreds of satellites in orbit around the Earth (in low-earth orbit). The satellites in each satellite constellation can be inter-connected through communication links to provide linked communication networks in the sky (e.g. in low-earth orbit). These inter-linked satellite communication networks may enable global communication coverage from any point on the planet (land, sea or air) to any other point on the planet by transmitting data across multiple satellites.

To provide desired throughput levels (e.g. throughput in excess of 10 Gb/s), satellites may include laser-based communication systems. To fully realize the potential of satellite communication networks, inter-satellite-links between each satellite and neighboring satellites would be desirable. In a typical configuration, each satellite in a network may be linked to a plurality of neighboring satellites in different directions (e.g. connected to four neighboring satellites for instance by a forward link, a bottom link, a left side link, and a right side link).

To provide the inter-satellite links, each satellite can be provided with multiple (e.g. four) optical signal terminals (that can be used for signal transmission/acquisition) also referred to herein as communication terminals. The terminals may be positioned at the corners of the satellite or in the middle. For each communication terminal, the satellite can include a telescope assembly to connect the external optics (e.g. the signal output/signal input optics) to internal communication systems. The signals from the telescope assembly can be aimed towards a neighboring satellite using a beam deflector (e.g. a coarse pointing assembly) provided by the corresponding communication terminal.

However, manufacturing four separate communication terminals, each having a separate high precision optical telescope, separate support structures, and separate mounting is expensive and requires high levels of manufacturing precision and testing. In addition, providing four separate telescope assemblies (along with the associated housing and mounting structures) is size and mass intensive, particularly for satellite applications.

Embodiments described herein may provide an optical system that includes a plurality of communication terminals. Each communication terminal can be independently controllable so that the terminals can be pointed in different directions (e.g. to target different neighboring satellites). Each communication terminal can be coupled to an internal aperture through a corresponding communication path.

However, rather than providing a separate telescope assembly for each terminal (and each communication path), the communication system can include a combined telescope assembly for all of the communication terminals (and communication paths). This telescope assembly can define a shared optical train that is used for each of the communication terminals/communication paths.

The shared telescope assembly may help reduce the size and mass requirements for the set of communication paths. In addition, the shared optical train may enable a simplified and less costly manufacturing and testing process.

Referring now to FIG. 1A, shown therein is an example telescope assembly 100 in accordance with an embodiment. Telescope assembly 100 may be used in various optical systems, such as an optical communication system or an optical imaging system. Telescope assembly 100 may provide a shared optical train for a plurality of signal paths.

For example, telescope assembly 100 may be used in an optical communication system such as an optical laser communication system used in a satellite. The telescope assembly 100 may provide an optical laser communication system with a shared optical train for a plurality of communication signal paths (e.g. for a plurality of communication links to neighboring satellites). In the example of FIG. 1A, each communication path may be represented by the corresponding communication path signal 120 a-120 d.

Each communication path can be coupled to a corresponding external communication terminal. Each external communication terminal may be operable to point in different directions (e.g. along different axes) while using the same shared optical train to transmit optical signals within the laser communication system. This may help reduce the size and mass of the optical communication system while permitting communication with multiple other systems arranged in different locations. This may be particularly advantageous in satellite applications, to facilitate inter-satellite-links while reducing the optical communication payload for each satellite.

As shown in FIG. 1A, the telescope assembly 100 can be coupled to a plurality of internal apertures 114 a-114 d. The internal apertures 114 a-114 d may be coupled to internal processing and/or control components. For example, the internal apertures 114 a-114 d may be coupled to internal communications components of a communication system, e.g. through fiber-optic links. An example of communication components that may be coupled to the internal apertures 114 a-114 d is shown in FIG. 11 and described herein below.

Each internal aperture 114 can be configured to communicate (e.g. receive or transmit) a corresponding aperture-specific optical signal 120 a-120 d. The aperture-specific optical signal 120 can be the optical signal received through, or to be transmitted through, a corresponding communication terminal. The direction of each corresponding communication terminal may be independently controllable. This may allow the optical signals from the internal apertures 114 to be communicated in (e.g. transmitted to or received from) different directions.

In the example illustrated, the telescope assembly is coupled to four internal apertures 114 a-114 d, although a different number of internal apertures may be provided in other embodiments of an optical system. The number of internal apertures 114 may be defined to correspond to the number of external communication terminals desired for an optical communication system.

System 100 can also include a plurality of external optical assemblies. The external optical assemblies can be configured to transmit and/or receive signals from external locations and/or systems. For example, the external optical assemblies may be configured to communicate with external communication systems such as other satellites. Alternately or in addition, the external optical assemblies may be configured to acquire signals from specified locations (e.g. images of specific locations). The external optical assemblies may include the external communication terminals as well as the optical components used to direct signals through those external terminals.

In FIG. 1A, representative external apertures 102 a-102 d are illustrated to indicate an example of the position of each aperture coupling to each external optical assembly. That is, each representative aperture 102 a-102 d provides an indication of where the telescope assembly 100 can be connected to a corresponding external optical assembly. Each representative aperture 102 a-102 d may correspond to an optical head unit of the corresponding external optical assembly (see e.g. FIG. 10 for example).

Each external optical assembly may correspond to a particular one of the internal apertures 114 a-114 d. Communication paths represented by signals 120 a-120 d shown in FIG. 1 are an example of a plurality of communication paths between internal apertures 114 a-114 d and corresponding external optical assemblies (represented by apertures 102 a-102 d). As shown in FIG. 1, the telescope assembly 100 includes four communication paths 120 a-120 d corresponding to four external communication terminals, although other numbers of communication paths may be used in different implementations. In some cases, multiple signals (e.g. one or more transmitted and/or received signals) may be communicated concurrently (e.g. through the use of various signal modulation techniques) through an individual communication path 120.

Each external optical assembly may be configured to direct the aperture-specific optical signals from the corresponding internal aperture 114 in a corresponding external direction. Each external optical assembly may be configured to transmit outgoing aperture-specific optical signals from a corresponding internal aperture 114 through an external communication terminal along the corresponding external direction. The external optical assembly and telescope assembly 100 can be configured to direct the outgoing aperture-specific optical signals received from the corresponding internal aperture 114 to be output in the corresponding external direction.

Each external optical assembly may also be configured to receive incoming aperture-specific optical signals through the external communication link from the corresponding external direction. The external optical assembly and telescope assembly 100 can be configured to direct the incoming aperture-specific optical signals received from the corresponding external direction to the corresponding internal aperture 114.

The telescope assembly 100 can be configured to direct aperture-specific optical signals between each internal aperture 114 and the corresponding external optical assembly (e.g. apertures 102). The telescope assembly can define a shared optical train for the plurality of internal-apertures 114 a-114 d.

The external direction for each external optical assembly may be independently controllable. This may allow the internal apertures 114 a-114 d to communicate with signals in different directions. The external optical assembly corresponding to each internal aperture 114 may be configured to communicate in an external direction that is spaced apart from every other external direction by a defined angular separation.

For example, the telescope assembly 100 may define a telescope field of view. Each external direction may be adjustable to an angular separation from each and every other external direction that is greater than the telescope field of view. This may allow the communication system (and associated satellite) to communicate with multiple different neighboring systems. Each external direction may be adjustable through a range of angular directions. The external directions may be adjusted to target different communication systems (e.g. neighboring satellites) and/or locations of interest (e.g. imaging locations). The range of angular directions for each communication terminal may vary in different embodiments.

The telescope assembly 100 can be positioned between the plurality of internal apertures 114 and the corresponding external optical assemblies (as shown by sub-apertures 102). The telescope assembly can include an optical train (i.e. a sequence of optical components) usable to direct optical communication signals between each input aperture 114 and the corresponding external optical assembly (as shown by sub-apertures 102). As shown in FIGS. 1A and 1B, the telescope assembly 100 can define a shared optical train for all of the communication paths 120 a-120 d.

The telescope assembly can be configured as a reflecting telescope including a plurality of mirrors. In some examples, the telescope assembly may be configured as an afocal telescope as shown.

As shown in FIGS. 1A and 1B, the optical train can include a first mirror 104, a second mirror 108, a series of lenses 110 and 116, a beam splitter 112 and an internal coupling component 114 (shown as a fast steering mirror in the example of FIG. 1B). Alternately, different configurations of the optical train may be implemented using only mirrors (see e.g. FIGS. 2 and 4) or using only lenses, or various other combinations of at least one lens and at least one mirror.

Each external optical assembly can include an input sub-aperture 102 (e.g. an optical head unit) arranged facing the first mirror 104. As shown in FIG. 1A, the first mirror 104 can be a parabolic mirror. Each input sub-aperture 102 a-102 d can be arranged to direct the corresponding incoming aperture specific optical signal to the same parabolic mirror 104 (or receive the corresponding outgoing aperture specific optical signal from that same parabolic mirror 104).

The optical train can also include a second mirror 108. As shown in FIG. 1B, the second mirror 108 may be an aspherical mirror. The second mirror 108 can be positioned to direct optical signals between the first mirror 104 and the lens sequence 110/116. The use of lens sequence 110/116 in place of a third mirror may further reduce the size of the telescope assembly 100.

The lens sequence 110/116 can include a spherical field lens 110 and a beam collimator lens 116. Each lens 110/116 may be provided as a spherical lens as shown in the example of FIG. 1B.

The beam splitter 112 can be positioned between the lens sequence 110/116 and the plurality of internal apertures 114 a-114 d. The beam splitter 112 can direct the corresponding optical signals to/from the corresponding input apertures 114. As shown in the example of FIGS. 1A and 1B, respective fast steering mirror 115 can be provided to further direct the optical signals towards the respective input apertures 114.

Various types of beam splitters 112 may be used. For example, a pyramid splitter, such as a metallized pyramidal prism, may be used as the beam splitter as shown in the example of FIG. 1B. Alternately, mirror-based beam splitters may be used.

The plurality of optical components in the shared optical train can be arranged about a central telescope axis. Each of the optical components (e.g. first mirror 104, second mirror 108, and lenses 110 and 116 in the example of FIGS. 1A and 1B) in the shared optical train can be positioned concentrically with the central telescope axis. The optical components can also be rotationally symmetric (e.g. about the central telescope axis). This may simplify the process of manufacturing the optical components of system 100.

By providing a shared optical train for each aperture-specific optical signal 120 a-120 d, the overall size and mass of the optical components required by the system 100 can be reduced. While the optical components in system 100 may be larger than those required for an optical train for one individual aperture-specific optical signal 120 a-120 d, the total size of system 100 can be significantly less than the combined size and mass of multiple individual optical trains.

In addition to reducing the size of the optical components, providing a shared optical train may also reduce the size and mass of other components, such as housings, support structures, heating/cooling elements, control signal lines and so forth required for the optical system. For example, the optical system may be provided within a combined housing as shown in the example of FIGS. 6-10 described herein below. This may allow the communication terminals to share housing and support structures, and share heating/cooling elements. Sharing of the heating/cooling elements may also reduce the power consumption required by the communication system, by heating one housing rather than four separate housings.

The control components of the communication system may similarly be simplified. In addition, the distance over which control cables need to be routed can be reduced, which may provide particular advantages for applications such as satellites.

Providing an optical system for a plurality of communication terminals that includes a shared optical train can also simplify the manufacturing and testing process, and reduce manufacturing costs. Overall costs can be reduced by required only one set of high precision optics that is shared by the plurality of communication terminals. In addition, a single support structure and a single temperature and mechanical isolation assembly can be shared by each of the communication terminals. The reduced part count both reduces costs (by reducing the number of high precision optical elements required) and helps facilitate high volume manufacturing. Rather than having to separately manufacture and align multiple telescope assemblies, a combined telescope assembly can be manufactured and aligned thereby providing multiple aligned telescope sections (see e.g. FIG. 3).

In some examples, the mirrors used in the optical train, such as the first mirror 104, may be manufacturing using a single point diamond turning (SPDT) process. SPDT is a common manufacturing method for metallic mirrors. SPDT provides greater fidelity to a desired surface form when the mirror being manufactured is a rotationally symmetric, on-axis mirror. Thus, manufacturing a single, rotationally symmetric, on-axis mirror 104 that is shared by multiple communication paths (in place of multiple off-axis mirrors) can provide more cost effective and higher performance manufacturing of the optical train as compared to individually machining multiple sets of optical components. In addition, as each individual telescope section can be configured as off-axis telescopes, central obstruction can be avoided by using multiple mirror sections 106 a-106 d off-axis (e.g. corresponding to input apertures 102 a-102 d). Thus, each communication path may in effect use an off-axis telescope assembly section 200 of the telescope assembly 100 as shown in FIG. 3 and described herein below.

Similar techniques can also be used to manufacture the other mirror components of the optical train, e.g. using SPDT.

Furthermore, testing and validation of the optical components can be simplified, as only many fewer components may require testing (e.g. ¼ of the number of optical components in a four terminal configuration).

Referring now to FIG. 2, shown therein is another example of a telescope assembly 100 that may be used in accordance with an embodiment. The telescope assembly 100 shown in FIG. 2 is generally similar to the assembly shown in FIG. 1B, except that the optical train is implemented entirely with mirrors. Thus, in place of the lenses 110 and 116, the telescope assembly 100 shown in FIG. 2 includes a third mirror 122. This may reduce chromatic aberrations for the optical communication system.

In addition, in contrast with the assembly shown in FIG. 1B, the splitter 112 is positioned between the third mirror 122 and the second mirror 108. The splitter 112 shown in FIG. 2 may be inverted as compared to the splitter 112 shown in the embodiment of FIGS. 1A and 1B. As with the splitter 112 shown in FIGS. 1A and 1B, various types of splitters may be used in the embodiment of FIG. 2. For example, fold mirrors may be used as the splitter 112 as shown in the example of FIG. 2.

As with the telescope assembly 100 shown in FIGS. 1A and 1B, the mirrors used in the telescope assembly 100 of FIG. 2 can be rotationally symmetric. Similarly, the mirrors used in the telescope assembly 100 of FIG. 2 can be concentric with each other.

As with the telescope assembly 100 shown in FIGS. 1A and 1B, the mirrors used in the telescope assembly of FIG. 2 may be machined using Single Point Diamond Turning.

Referring now to FIG. 3, shown therein is a telescope assembly section 200 of the telescope assembly 100 shown in FIG. 2. The telescope assembly section 200 shown in FIG. 3, illustrates an optical train section corresponding to a single input aperture 114 c and corresponding external optical assembly (represented by input aperture 102 c). Each input aperture 114 (and corresponding external optical assembly) in the telescope assembly 100 may have a corresponding optical train section such as the section 200 shown in FIG. 3.

As shown in FIG. 1A, a single on-axis mirror 104 can be shared for each external communication terminal (represented by apertures 102 a-102 d). As shown in FIG. 3, the optical train assembly can operate as separate telescope assembly sections 200 for each external optical assembly/internal aperture 114. While the overall telescope assembly 100 may be provided with an on-axis mirror 104, each telescope section 200 may in effect provide an off-axis mirror section 106 a-106 d for the corresponding optical train section.

As shown in FIG. 3, the optical train section of the telescope section 200 corresponding to the individual sub-aperture 102 c can be generally analogous to an independent off-axis telescope assembly. In the example illustrated, the optical train section includes a first mirror section 106 c (corresponding to a portion of first mirror 104), a second mirror section 108 c (corresponding to a portion of second mirror 108), and a third mirror section 122 c (corresponding to a portion of third mirror 122).

Each communication path (e.g. each signal path between an internal aperture 114 and corresponding aperture 102/external optical assembly) may have a corresponding optical train section that includes a specific portion of each optical train element (e.g. first mirror 104, second mirror 108, and third mirror 122) for that communication path. The portion of each optical train element for a given communication path may be separate from the portion of each optical train element for each and every other communication path using the shared optical train. Each communication path may nonetheless include the same sequence of optical train elements with the signals along those communication paths interacting with different segments or sections of the optical train elements. The different communication paths can be non-intersecting between each internal aperture 114 and corresponding aperture 102.

Alternate optical train section configurations may be provided depending on the configuration of the telescope assembly 100, e.g. using different combinations of mirrors and/or lenses. In different configurations of the telescope assembly 100, the plurality of communication paths may share optical train elements while interacting with different portions of each optical train element.

The optical train section can also include a splitter section 112 and the corresponding aperture 114 c. The first mirror section 106 c, second mirror section 108 c, and third mirror section 122 c can be configured to provide an afocal telescope assembly for the communication path 120 c between internal aperture 114 c and the corresponding external optical assembly.

In the example illustrated, the first mirror section 106 c operates as an off-axis parabolic mirror section for the optical train section. In the telescope assembly section 200, the first mirror section 106 c is provided by a sub-aperture of the on-axis mirror 104. Although the overall larger telescope assembly 100 may be rotationally symmetric and may correspond to an on-axis telescope, in operation it can be used as a set of off-axis telescopes (e.g. four off-axis telescopes) as shown in FIG. 3. Each off-axis telescope section can be coupled to a corresponding external optical assembly whose communication direction can be independently controlled. For instance, the external optical assembly corresponding to each off-axis telescope section can have an independent pointing range (e.g. an independent range for the corresponding external direction) that can be controlled, e.g. through a beam deflector arrangement. For example, each external optical assembly may include a coarse pointing assembly usable to adjust the external direction for that communication path.

Each communication path may also include a fine pointing assembly proximate the corresponding internal aperture. The fine pointing assembly may be provided as an internal jitter stabilization device operable to perform small adjustments of the communication path proximate the internal aperture 114. The movements performed by the fine pointing assembly may be defined to remain well within the telescope field of view of telescope assembly 100.

Referring now to FIG. 4 shown therein is another example of a telescope assembly 100 that may be used in accordance with an embodiment. The telescope assembly 100 shown in FIG. 4 is generally similar to the assembly shown in FIG. 2, except that the splitter 112 is provided on the second mirror 108. The second mirror 108 may also include a final folding mirror usable to direct communications to/from the corresponding internal aperture. This may further reduce the number of components in the telescope assembly 100, and allow the telescope assembly 100 to be even more compact. For example, the splitter 112 can be incorporated into the second mirror 108 through the single-point diamond turning process.

Referring now to FIG. 5, shown therein is an example of a terminal section 300 of an optical communication system. The terminal section illustrates the configuration of the portion of the optical communication system corresponding to an individual communication terminal. Terminal section 300 shown in FIG. 5 is an example of a single communication terminal in which the telescope assembly is specific to that terminal. However, the components of the terminal section 300 apart from the individual telescope assembly section may be used in accordance with embodiments described herein.

In the example illustrated, the terminal section 300 extends between an external communication opening (or aperture) 320 and internal couplings (not shown) connected to a fine pointing assembly 330. As shown, the terminal section 300 includes a coarse pointing assembly 310, a telescope assembly section (including first mirror 304, second mirror 308, and third mirror 322), and a fine pointing assembly 330. Optical signals 320 a can be transmitted between the opening 320 and the input couplings via the coarse pointing assembly 310, telescope assembly, and fine pointing assembly 330.

Optical signals (e.g. laser light) can be directed via fiber couplers (not shown) into the fine pointing module 330. The optical signals can then be directed to the telescope assembly, where it can be magnified (e.g. by 13.3× in the illustrated example). The magnified optical signals can then be directed through the coarse pointing assembly 310. The magnified light can then contact the mirror 315 and exit the coarse pointing assembly 310 through opening 320.

The reverse process can be performed for incoming aperture-specific signals arriving at the opening 320 of each communication terminal. Optical signals (e.g. laser light) can be received through opening 320 and contact the mirror 315 where it is redirected through the coarse pointing assembly 310 to the telescope assembly. The optical signals can then be de-magnified and directed into the fine pointing module 330. The optical signals can then be coupled into control and/or processing systems, e.g. through fiber couplings.

In the example illustrated, the coarse pointing assembly 310 is an example of an external optical assembly that may be used with a communication system that includes telescope assembly 100. The coarse pointing assembly 310 can be actuated to control the external communication direction of the corresponding communication path.

Each communication path in a communication system including telescope assembly 100 can be configured to travel through an independently actuated coarse pointing assembly 310. More generally, in embodiments including telescope assembly 100, each communication path may be directed through an independently controllable beam deflector that is adjustable to define the external communication direction of the corresponding communication path.

Each communication path in a communication system including telescope assembly 100 can also include an independent fine pointing assembly 330. However, in contrast with the example shown in FIG. 5, each communication path 120 can share the same telescope assembly 100 and optical train. Accordingly, the components of each communication path 120 a-120 d may be contained within a single main housing and assembly (see e.g. FIGS. 6 to 10). This may also facilitate more rapid manufacturing and simpler alignment of the optical components.

Referring now to FIGS. 6 to 10, shown therein is an example of an optical system assembly 400. As shown in FIG. 6, an optical communication system 400 can include a plurality of communication paths contained within a combined housing assembly 405. Each communication path can extend between a communication terminal having an external aperture 320 and an internal aperture 114. As shown in the example illustrated, each external aperture 320 may be provided through a periscope 410 provided on the top of housing 400.

The combined housing assembly 400 can include a directional assembly for each communication path (e.g. coarse pointing assembly 310 and a fine pointing assembly such as fine pointing assembly 330). In addition, a shared telescope assembly 100 can be contained within the combined housing assembly 400 (see e.g. FIG. 10). The shared telescope assembly can include an optical train that is shared by each of the communication paths. As noted above, the optical train may be shared by each of the communication paths while signals in each communication path interact with distinct sections of each optical component in the optical train.

As with the terminal section 300, each communication path 120 in the optical communication system 400 can include an external optical assembly with an adjustable beam deflector. In the example illustrated, the beam deflector is provided in the form of a coarse pointing assembly 310. The external optical assembly (e.g. coarse pointing assembly 310) can be configured to receive an outgoing optical signal via an input aperture (e.g. apertures 102) and direct the optical signal towards the corresponding output terminal. The external optical assembly (e.g. coarse pointing assembly 310) can also be configured to receive an incoming optical signal via the output terminal and direct the optical signal towards the corresponding input aperture (e.g. apertures 102). The coarse pointing assembly 310 and output terminal may be adjusted to adjust the external communication direction of each communication path. For example, mirror 315 may be rotatable to provide a coarse pointing periscope.

Each external optical assembly may be adjustable between a range of angular directions. The range of angular directions can allow each external optical assembly to point towards a range of locations external to the optical system. For example, each external optical assembly may be adjustable through an angular range of about 120 degrees (e.g. a +/−60° azimuth range). The specific angular range of each external optical assembly may vary depending on the particular implementation. For example, the size of the overall communication system may be adjusted to account for desired angular ranges (e.g. the size may be increased to increase the angular range available to each external optical assembly). For example, for a configuration with an angular range of +/−95° (190° total azimuth range), the size of the overall communication system assembly may be approximately 25% larger than that required for a +/−60° azimuth range.

Alternately or in addition, each external optical assembly may be adjustable between a plurality of elevation angles within an elevation angular range. For example, each external optical assembly may be adjustable between elevation angles within an elevation angular range of about +/−15°.

Each external optical assembly may be independently adjustable in two dimensions (e.g. through an azimuthal angular range and an elevation angular range).

Although for ease of exposition, telescope assembly 100 and combined assembly 400 are described herein in the context of an optical communication system it should be understood that telescope assembly 100 and combined assembly may also be used in various other optical systems, such as optical imaging systems. For example, optical imaging systems may be provided in which image capture devices (e.g. cameras) are coupled to the input apertures 114 to allow a combined device to image multiple fields in different directions simultaneously. In such an example, each external optical assembly may be adjustable to point in a corresponding desired imaging direction.

Referring now to FIG. 11, shown therein is an example of a signal transceiver unit 500 in accordance with an embodiment. Signal transceiver unit 500 may be used with an optical system that includes a telescope assembly such as telescope assembly 100 and/or combined assembly 400. For example, signal transceiver unit 500 may be used to provide an optical laser communication system.

As shown in FIG. 11, signal transceiver unit 500 can include a signal transmission path 510 and a signal reception path 520. The signal transmission path 510 and signal reception path 520 are coupled to an input aperture 114. The input aperture 114 can couple signals between the optical train of telescope assembly 100 and the signal transmission path 510 and signal reception path 520. Depending on the particular implementation of an optical system, a signal transceiver unit may be configured with only one of the signal transmission path 510 and signal reception path 520.

As shown in FIG. 11, the signal transmission path 510 and signal reception path 520 are coupled to a modem 502. The modem 502 can be configured to perform various signal processing operations on the outgoing signal(s) to be transmitted through signal transmission path 510 and/or the incoming signal(s) received through signal reception path 520.

The signal transceiver unit 500 can be configured to convert the signals between an optical form (for transmission through the telescope assembly and external optical assembly) and alternate formats that may be used for internal transmission and/or communication to devices using other communication formats, such as Ethernet or radio-frequency formats for example.

Transmission unit 512 can be configured to convert outgoing signals from an alternate communication and/or processing format (e.g. Ethernet) into optical signals. The transmission unit 512 can be configured to modulate outgoing signals for transmission as an optical laser signal along signal transmission path 510. For example, transmission unit 512 may include a laser light source. Transmission unit 512 may also include an external or integrated optical modulator such as an electro-absorption modulator (EAM) or a Lithium Niobate Mach Zehnder external modulator for example. The optical modulator may be operable to modulate the laser light source to generate an outgoing optical laser signal to be transmitted along the signal transmission path 510 to aperture 114.

The outgoing optical laser signal can be further processed along the signal transmission path 510 before reaching the aperture 114 (i.e. before passing through telescope assembly 100). For example, an optical amplifier 514 may be provided along the signal transmission path 510 to amplify the outgoing optical signals prior to entering the telescope assembly 100.

Reception unit 526 can be configured to convert incoming signals from optical signals into an alternate communication and/or processing format (e.g. Ethernet). The reception unit 526 can be configured to demodulate incoming optical laser signal(s) received through signal reception path 520. For example, the reception unit 526 can include a photodiode. Incoming optical signals can be received by the photodiode and a corresponding electrical signal can be generated in response. Reception unit 526 may also include various electrical signal processing components, such as an electrical amplifier and/or one or more signal filters (e.g. a bandpass filter).

The incoming optical laser signal may be further processed along the signal reception path 520 before reaching the reception unit 526. For example, the incoming optical signals may pass through an optical amplifier 522 after being received through aperture 114 (i.e. after passing through telescope assembly 100). The optical amplifier 522 can amplify the incoming optical signal before it reaches reception unit 526. The incoming optical signals may also pass through an optical filter 524. For example, optical filter 524 may be a bandpass optical filter. The optical filter 524 can be defined to remove noise and/or background signal components in the incoming optical signal before it reaches reception unit 526.

In some examples, the transmission unit 512 and reception unit 526 may be implemented using a combined transceiver module.

Modem 502 may be configured to perform various processing operations on the incoming and outgoing signals passing therethrough. For example, the modem 502 can be configured to perform various forward error correction operations on the incoming and/or outgoing signals.

Although the aperture 114 is shown as being separately coupled to the signal transmission path 510 and the signal reception path 520, it should be understood that additional optical components (e.g. beam splitters) may be used to provide a combined signal path that extends between the transmission path 510 and reception path 520 and aperture 114.

In some examples, the transceiver unit 500 may be configured to concurrently transmit/receive multiple signals along the signal transmission path 510 and the signal reception path 520 respectively.

In some examples, various signal modulation techniques (e.g. wavelength division multiplexing, polarization multiplexing etc.) may be used to allow multiple different signals to be communicated along a shared signal path (e.g. multiple signals may be concurrently transmitted along the signal transmission path 510, signal reception path 520, and/or a combined signal path).

While the above description provides examples of the embodiments, it will be appreciated that some features and/or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. Accordingly, what has been described above has been intended to be illustrative of the invention and non-limiting and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the invention as defined in the claims appended hereto. The scope of the claims should not be limited by the preferred embodiments and examples, but should be given the broadest interpretation consistent with the description as a whole. 

The invention claimed is:
 1. An optical system comprising: a plurality of internal apertures operable to receive a plurality of aperture-specific optical signals, wherein each internal aperture is operable to receive a corresponding aperture-specific optical signal of the plurality of aperture-specific optical signals; a plurality of external optical assemblies, wherein each external optical assembly corresponds to one of the internal apertures, and each external optical assembly is operable to direct the corresponding aperture-specific optical signal of the corresponding internal aperture in a corresponding external direction, wherein the external direction for each external optical assembly is independently controllable; and a telescope assembly positioned between the plurality of internal apertures and the plurality of external optical assemblies, wherein the telescope assembly defines a single shared optical train arranged to direct the plurality of aperture-specific optical signals between the plurality of internal apertures and the plurality of external optical assemblies, wherein the shared optical train is arranged to direct the aperture-specific optical signals between each internal aperture and the corresponding external optical assembly, wherein the shared optical train includes a plurality of individual optical elements arranged into an optical sequence whereby each aperture-specific optical signal is directed to each optical element in the plurality of individual optical elements in the optical sequence as that aperture-specific optical signal travels between the corresponding internal aperture and corresponding external optical assembly.
 2. The optical system of claim 1, wherein the telescope assembly defines a central telescope axis, and the optical train is rotationally symmetric about the central telescope axis.
 3. The optical system of claim 1, wherein the optical train comprises a plurality of optical elements, and the plurality of optical elements are concentric.
 4. The optical system of claim 1, wherein the optical train comprises a plurality of mirrors, wherein the plurality of mirrors are concentric.
 5. The optical system of claim 1, wherein the optical train comprises a plurality of lenses, wherein the plurality of lenses are concentric.
 6. The optical system of claim 1, wherein the optical train comprises a plurality of mirrors, wherein each mirror is rotationally symmetric.
 7. The optical system of claim 1, wherein the optical train comprises a plurality of lenses, wherein each lens is rotationally symmetric.
 8. The optical system of claim 1, wherein the optical train comprises at least one lens and at least one mirror wherein the at least one lens and the at least one mirror are concentric.
 9. The optical system of claim 1, wherein the optical train comprises at least one lens and at least one mirror wherein each lens and each mirror is rotationally symmetric.
 10. The optical system of claim 1, wherein: the telescope assembly defines a telescope field of view; and each external direction has an angular separation from each and every other external direction that is controllable to an angular separation range greater than the telescope field of view.
 11. The optical system of claim 1, wherein each external optical assembly comprises an adjustable beam deflector operable to direct the corresponding aperture-specific optical signal through a corresponding external communication terminal in the corresponding external direction.
 12. The optical system of claim 11, wherein the beam deflector comprises a coarse pointing assembly.
 13. The optical system of claim 1 wherein the optical system is an optical laser communication system.
 14. The optical system of claim 1 wherein the telescope assembly includes a single primary mirror and a single secondary mirror.
 15. An optical system comprising: a plurality of internal apertures, wherein each internal aperture is operable to receive a corresponding aperture-specific optical signal; a plurality of external optical assemblies, wherein each external optical assembly corresponds to one of the internal apertures, and each external optical assembly is operable to direct the aperture-specific optical signal of the corresponding internal aperture in a corresponding external direction, wherein the external direction for each external optical assembly is independently controllable; and a telescope assembly positioned between the plurality of internal apertures and the plurality of external optical assemblies, wherein the telescope assembly defines a shared optical train arranged to direct the aperture-specific optical signals between each internal aperture and the corresponding external optical assembly, wherein the shared optical train comprises a single concave parabolic mirror, and each external optical assembly comprises an input sub-aperture arranged facing the single concave parabolic mirror whereby each corresponding aperture-specific optical signal is reflected by the single concave parabolic mirror.
 16. The optical system of claim 15, wherein the telescope assembly defines a central telescope axis, and the parabolic mirror is concentric with the central telescope axis and the parabolic mirror is rotationally symmetric about the central telescope axis.
 17. The optical system of claim 15 wherein the telescope assembly includes a single primary mirror and a single secondary mirror.
 18. An optical system comprising: a plurality of internal apertures operable to receive a plurality of aperture-specific optical signals, wherein each internal aperture is operable to receive a corresponding aperture-specific optical signal; a plurality of external optical assemblies, wherein each external optical assembly corresponds to one of the internal apertures, and each external optical assembly is operable to direct the aperture-specific optical signal of the corresponding internal aperture in a corresponding external direction, wherein each external optical assembly is operable to adjust the external direction along which the aperture-specific optical signal of the corresponding internal aperture is directed, and each external optical assembly is independently controllable to adjust the corresponding external direction; and a telescope assembly positioned between the plurality of internal apertures and the plurality of external optical assemblies, wherein the telescope assembly defines a shared optical train arranged to direct the plurality of aperture-specific optical signals between the plurality of internal apertures and the plurality of external optical assemblies, wherein the shared optical train is arranged to direct the aperture-specific optical signals between each internal aperture and the corresponding external optical assembly.
 19. The optical system of claim 18 wherein: the telescope assembly defines a telescope field of view; and each external optical assembly is adjustable to direct the aperture-specific optical signal of the corresponding internal aperture through a range of potential external directions, wherein the range of potential external directions includes external directions with an angular separation from each and every other external direction of every other external optical assembly that is greater than the telescope field of view.
 20. The optical system of claim 18 wherein the telescope assembly includes a single primary mirror and a single secondary mirror. 